[0001] It is known to produce N-acyl-acyloxy aromatic amines, e.g. 4-acetoxyacetanilide,
by preparing the sodium salt of the corresponding N-acyl- hydroxy aromatic amine,
e.g. N-acetyl-para-aminophenol (APAP), and reacting the sodium salt with the appropriate
carboxylic acid anhydride, e.g. acetic anhydride. The N-acyl-hydroxy aromatic amine,
e.g. APAP, used as the starting material for the foregoing reaction is in turn prepared
by acylating the corresponding hydroxy aromatic amine, e.g. para-aminophenol, with
an acylating agent such as an anhydride, e.g. acetic anhydride. However the latter
reaction may cause problem such as the difficulty of mono-acylating the hydroxy aromatic
amine, oligomerization of the hydroxy aromatic amine, and color body formation.
[0002] Furthermose, when APAP is produced from para-aminophenol, nitro-benzene typically
is catalytically hydrogenated and concomitantly rearranged in the presence of a platinum
catalyst to produce the para-aminophenol, presenting the problem of recovering the
dissolved platinum catalyst.
[0003] It is also known to prepare APAP by hydrogenating 4-nitro-chlorobenzene to a 4-chloroaniline
which is then reacted with aqueous KOH to form para-aminophenol. This is then acetylated
as described previously to form the N-acetyl-para-aminol. This process is relatively
complex requiring a fair number of reaction and purification steps. Moreover, the
acetylation step in this process is believed to give rise to the same problems as
occurs in the acetylation step of the nitrobenzene process described previously.
[0004] The preparation of hydroxy aromatic ketones by the Fries rearrangement of aromatic
esters is well-known in the art. Thus, Lewis, U.S. Patent No. 2,833,825 shows the
rearrangement of phenyl or other aromatic esters to acylphenols or other hydroxy aromatic
ketones using anhydrous hydrogen fluoride as catalyst. The examples of this patent
are limited to the rearrangement of esters of higher fatty acids with the yields ranging
from 55 to 95%.
[0005] Simons et al, Journal of the American Chemical Society, 62, 485 and 486 (1940) show
the use of hydrogen fluoride as a condensing agent for various rearrangements and
at page 486 show the Fries rearrangement of phenyl acetate to obtain p-hydroxyacetophenone.
[0006] Dann and Mylius in a dissertation included as part of a series of Reports from the
Institute for Applied Chemistry of the University of Erlangen, received for publication
on January 7, 1954 and published in Annalen der Chemie 587 Band, pages 1 to 15 (1954),
show the rearrangement of phenyl acetate in hydrogen fluoride to 4-hydroxyacetophenone,
with a maximum yield of 81% after 24 hours of reaction time, and report a yield of
92% stated to be obtained by K. Weichert as reported in Angewandte chemie 56, 338
(1943) . However, Dann and Mylius suggest that the difference in yields may be at
least partly due to the previous ignoring by Weichert of the accompanying 2-hydroxyacetophenone.
[0007] Dann and Mylius also disclose the reaction of phenol and glacial acetic acid in the
presence of hydrogen fluoride to produce 4-hydroxyacetophenone at a yield of 61.6%.
This reaction may be conventionally characterized as a Friedel-Crafts acetylation
of phenol with acetic acid as the acetylating agent.
[0008] Simons et al, Journal of the American Chemical Society, 61, 1795 and 1796 (1939)
teach the acylation of aromatic compounds using hydrogen fluoride as a condensing
agent and in Table Ion page 1796 show the acetylation of phenol with acetic acid to
produce p-hydroxyacetophenone in 40% yield.
[0009] Meussdoerffer et al, German Offenlegungsschrift 26 16 986 published October 27, 1977
and assigned to Bayer AG, disclose the acylation of phenolic compounds such as phenol
itself with an acyl halide such as acetyl chloride to form hydroxy aromatic ketones.
[0010] Auwers et al, Chemische Berichte, 58, 36-51, (1925) show the Beckmann rearrangement
of a large number of oximes of aromatic ketones most of which are substituted acetophenones.
However, the only attempted rearrangement of the oxime of a ring-unsubstituted hydroxy
aromatic ketone was that of the oxime of o-hydroxyacetophenone, but no amine was formed,
i.e. the attempted rearrangement was unsuccessful; see page 41.
[0011] Ganboa et al, Synthetic Comunications 13 (11), 941-944 (1983) show the production
of acetanilide from acetophenone by refluxing in a solution of hydroxylamine hydrochloride.
There is however no suggestion of the synthesis of N-acylacyloxy aromatic amines such
as 4-acetoxyacetanilide (AAA) or of the synthesis of N-acylhydroxy aromatic amines
such as N-acetyl-para-aminophenol (APAP).
[0012] Pearson et al, Journal of the American Chemical Society 75 5905-5908 (Dec. 5, 1953)
disclose the formation of hydrazones from ketones by reaction with hydrazine hydrate
and the rearrangement of the hydrazone to the amide by reaction with sodium nitrite
and concentrated sulfuric acid. Specifically, on page 5907 Pearson et al show the
rearrangement of p-hydroxyacetophenone hydrazone to p-hydroxyacetanilide, i.e. APAP.
[0013] In accordance with one aspect of this invention, N-acyl-hydroxy aromatic amines,
e.g. N-acetyl-para-aminophenol (APAP), are produced by reacting a hydroxy aromatic
ketone, e.g. 4-hydroxyacetophenone (4-HAP), with a hydroxylamine salt, to form the
ketoxime of the ketone and subjecting the ketoxime to a Beckmann rearrangement in
the presence of a catalyst to form the N-acyl-hydroxy aromatic amine.
[0014] In one specific embodiment, N-acetyl-para-aminophenol (APAP), also know as acetaminophen,
is produced from phenyl acetate, or phenol and an acetylating agent such as acetic
acid, by means of an integrated process including the steps of converting the phenyl
acetate, or phenol and an acetylating agent, to 4-hydroxyacetophenone by a Fries rearrangement
or Friedel-Crafts acetylation respectively, and converting the 4-hydroxyacetophenone
to the corresponding ketoxime with hydroxylamine or a hydroxylamine salt. The ketoxime
is then subjected to a Beckmann rearrangement in the presence of a catalyst to form
the N-acetyl-para-aminophenol.
[0015] In accordance with another aspect of this invention, N-acyl-acyloxy aromatic amines,
e.g. 4-acetoxyacetanilide (AAA), are produced by reacting a hydroxy aromatic ketone,
e.g. 4-hydroxyacetophenone (4-HAP), with hydroxylamine or a hydroxylamine salt, to
form the ketoxime of the ketone and subjecting the ketoxime to a Beckmann rearrangement
and accompanying acylation by contacting the ketoxime with a carboxylic acid anhydride
and a Beckmann rearrangement catalyst to form the N-acyl- acyloxy aromatic amine.
[0016] In another specific embodiment, 4-acetoxyacetanilide (AAA) is produced from phenyl
acetate, or phenol and an acetylating agent such as acetic acid, by means of an integrated
process including the steps of converting the phenyl acetate, or phenol and an acetylating
agent, to 4-hydroxyacetophenone by a Fries rearrargement or Friedel-Crafts acetylation
respectively, and converting the 4-hydroxyacetophenone to the corresponding ketoxime
with hydroxylamine or a hydroxylamine salt. The ketoxime is then subjected to a Beckmann
rearrangement and accompanying acetylation by contacting the ketoxime with acetic
anhydride and a Beckmann rearrangement catalyst to form the 4-acetoxyacetanilide.
[0017] When carrying out the process of this invention using phenyl acetate as the starting
material, the initial Fries rearrangement to produce 4-3-hydroaxyacetophenone (4-HAP)
from phenyl acetate is defined by equation (I):

[0018] If phenol and an acetylating agent are used as the staring material, the resulting
acetylation reaction to form 4-HAP is indicated by equation (II):

where X is the residue minus an acetyl group of compounds which are known acetylating
agents. X may be, for example, hydroxy, acetoxy, or halide including fluoride, chloride,
bromide, or iodide. Acetylating agents which may be used are for example, acetic acid,
acetic anhydride, acetyl fluoride, acetyl chloride and acetyl bromide.
[0019] The ketoxime formation of this invention proceeds as indicated in equation (III)
:

[0020] The formation of the ketoxime of 4-HAP, i.e. 4-HAP oxime, proceeds as in equation
(IV):

[0021] When N-acyl-hydroxy aromatic amines are the desired product, the Beckmann rearrangement
of this invention proceeds as in equation (V):
while the Beckmann rearrangement when APAP is the desired product proceeds as in equation
(VI):

[0022] When N-acyl-acyloxy aromatic amines are the desired product, the Beckmann rearrangement
and accompanying acylation of this invention proceeds as in equation (VII):

while the Beckmann rearrangement and accompanying acetylation when AAA is the desired
product proceeds as in equation (VIII) :

[0023] In equations (III), (V), and (VII), Ar
l is a divalent aromatic radical. The specific nature of the radical is not critical
but it is preferably a radical resulting from the removal of two ring hydrogen atoms
from benzene, naphthalene, or biphenyl, either unsubstituted or with ring hydrogens
substituted with radicals such as alkyl, alkenyl, alkynyl, alkoxy or acyloxy containing
1 to 18 carbon atoms, aralkyl containing 7 to 18 carbon atoms; halogen, e.g. chlorine,
bromine, or iodine; hydroxy; amino; or sulfhydryl. Ar
1 is preferably 1,4-phenylene, 2,1-naphthylene, 2,6-naphthylene, 5-phenyl-1,2 phenylene,
3-phenyl-1,4-phenylene or 3 methyl-1,4-phenylene with the ketocarbon and corresponding
groups occupying the first stated numbered position of Ar
1 when the positions are not equivalent. Most preferably Ar
1 is 1,4-phenylene.
[0024] The R groups in the foregoing equations may be the same or different and are each
a monovalent organic radical containing, for example 1 to 18 carbon atoms preferably
1 to 4 carbon atoms. R may be, for example, alkyl, alkenyl, alkynyl, alkoxy, acyl
or acyloxy containing 1 to 18 carbon atoms, either unsubstituted or substituted with
radicals such as halogen, e.g. chlorine, bromine, or iodine; hydroxy; amino; sulfhydryl;
or an aryl radical, Ar which may be a monovalent radical corresponding to the definition
of Ar
1 given above except that the carbon bonded to OH is bonded to a hydrogen instead.
Preferably, R is the same in all occurrences in equations (III), (V), and (VII) and
is methyl, ethyl, propyl, or n-butyl and most preferably methyl corresponding to the
use of acetate esters and methyl ketones in the latter equations. The preferred specific
hydroxy aromatic ketone used to form the oxime is 4-hydroxyacetophenone (4-HAP) and
the preferred products are 4-acetoxyacetanilide (AAA) and N-acetyl-para-aminophenol
(APAP) .
[0025] The hydroxy aromatic ketone used to form the oxime may be prepared by any method
known in the art. For example, it may be prepared by the Fries rearrangement of the
corresponding aromatic ester as indicated by the following equation, which is a generalized
form of equation (I), where Ar, Ar
1 and R have the definitions given above:

[0026] Alternatively, a phenolic compound and an acylating agent may be reacted in a Friedel-Crafts
acylation to form the hydroxy aromatic ketone, in accordance with the following equation,
which is a generalization form of equation (II):

where Ar, Ar
1 and R have the meanings given previously and X is the

residue minus the acyl group, , of the compounds which are known acylating agents,
such as hydroxy, acyloxy, e.g. acetoxy, and halide, e.g. fluoride, chloride, bromide,
and iodide. Examples of phenolic compounds which may be employed are phenol, 1-naphthol,
2 naphthol, 2-phenylphenol, 4-phenylphenol and o-cresol. Acylating agents which may
be used are for example alkanoic acids, e.g. acetic and prcpionic acids, alkanoic
acid anhydrides, e.g. acetic and prcpionic anhydrides, and acyl halides, e.g. acetyl
and propionyl fluorides, chlorides, and branides. Note that although the reaction
of a phenolic compound and an acylatirg agent is characterized herein as a "Friedel-Crafts
acylation," no opinion as to the mechanism of reaction should be implied by this characterization.
[0027] The catalyst for both of the foregoing reactions is preferably hydrogen fluoride
but any other catalyst known in the art to be effective for the Fries and Friedel-Crafts
reactions may be used, e.g. aluminum chloride, zinc chloride, or boron trifluoride.
[0028] In carrying out the reaction, the aromatic ester or phenolic compound and acylating
agent, catalyst and if desired when an aromatic ester is the starting material, an
additive for the reaction such as acetic anhydride or acetic acid, may be charged
to a corrosion-resistant reactor and the mixture maintained at a temperature, for
example, of about 20 to about 100°C for a period, for example, of about 1/2 to about
4 hours, at a pressure, for example, of about 50 to about 500 psia (3.4 to 34 bar).
If HF is used as the catalyst it may be charged as a liquid or a gas using technologies
of handling well-known to those skilled in the art. In carrying out the reaction,
an inert gas such as nitrogen may be used to keep the reaction space under the desired
pressure and sufficient HF in contact with the reacting liquid. An excess of HF is
generally used, for example, about 7 to about 75 moles per mole of aromatic ester
or phenolic compound initially present in the reaction zone. If AAA or APAP is the
desired product of the reaction, the starting material if a Fries rearrangement is
employed will be phenyl acetate while phenol and an acetylating agent such as acetic
acid is the starting material if a Friedel-Crafts acylation is utilized. In both cases,
the starting material is converted to 4-HAP which is in turn converted by the process
of this invention to AAA or APAP.
[0029] The conversion of hydroxy aromatic ketones, e.g. 4-HAP, into N-acyl- acyloxy aromatic
amines, e.g. AAA, or into N-acyl-hydroxy aromatic amines, e.g., APAP, is accomplished
by first forming the ketoxime from the hydroxy aromatic ketone as indicated by equations
(III) and (IV), by contacting the ketone with hydroxylamine or a hydroxylamine salt,
e.g. hydroxylamine hydrochloride, hydroxylamine sulfate, hydroxylamine bisulfate,
or hydroxylamine phosphate, and a base, e.g. ammonium hydroxide, potassium hydroxide,
sodium hydroxide, or lithium hydroxide in an amount, for example, of 1 to 3 moles
per mole of hydroxylamine, at a temperature, for example of 0 to 60°C for a period,
for example, of 1 to 4 hours. Any pressure may be used, e.g. 80mm. of mercury to 10
atmospheres absolute (0.1 bar to 10.1 bar). The reaction is preferably carried out
in an aqueous or alcoholic medium, i.e. in the presence of water and/or an alcohol
such as methanol, ethanol, or isopropanol.
[0030] As discussed above, in accordance with one embodiment of the invention, the ketoxime
may be converted into the corresponding N-acyl-hydroxy aromatic amine by a Beckmann
rearrangement as shown in equations (V) and (VI), by contacting the ketoxime with
a catalyst for the reaction at a temperature, for example of -70°C to 118°C for a
period for example of ten minutes to 4 hours. The pressure is not critical and may
be, for example, in the range of 80 mm. of mercury to 10 atmospheres absolute (0.1
bar to 10.1 bar). Preferably, the rearrangement is conducted at a temperature of from
about -70°C to about 40°C and at a molar ratio of ketoxime to catalyst from about
1:0.001 to about 1:0.1, for a reaction time of about ten minutes at about two hours.
Any Beckmann rearrangement catalyst may be used, as for example, an acid, e.g. mineral
acid such as sulfuric or hydrochloric acid, an organic acid such as trifluoroacetic
acid, para-toluenesulfonic acid, benzenesulfonic acid or methanesulfonic acid, an
acidic ion-exchange resin such as Amberlyst 15 or Nafion 501 which are sulfonic acid
ion-exchange resins, or thionyl chloride in liquid sulfur dioxide, diethyl ether,
ethylacetate, acetone, tetrahydrofuran, or methylene chloride. Preferably the Beckmann
rearrangement is conducted with thionyl chloride in liquid sulfur dioxide. The reaction
may be advantageously carried out in the presence of the glacial carboxylic acid corresponding
to the N-acyl group of the desired product which will ordinarily yield the hydroxy
derivative. The total amount of glacial carboxylic acid is not critical but is usually
present such that the ketoxime concentration is in the range of 2 to 50% by weight
at the start of the reaction.
[0031] In accordance with another embodiment of the invention, the ketoxime may be converted
into the corresponding N-acyl-acyloxy aromatic amine by a Beckmann rearrangement and
accompanying acylation as shown in equations (VII) and (VIII), by contacting the ketoxime
with the appropriate carboxylic acid anhydride and a Beckmann rearrangement catalyst
at a temperature, for example of 0 to 118°C for a period for example of 1 to 4 hours.
As defined in the foregoing equations, any of a broad class of anhydrides may be used
but the anhydride is preferably that of an alkanoic acid containing 2 to 4 carbon
atoms, e.g. acetic anhydride, propionic anhydride, or n-butyric anhydride. The pressure
is not critical and may be, for example, in the range of 80 mm. of mercury to 10 atmospheres
absolute (0.1 to 10.1 bar). Again, any Beckmann rearrangement catalyst may be used,
as discussed above. The reaction may be advantageously carried out in the presence
of the glacial carboxylic acid corresponding to the anhydride employed in the reaction
in an amount, for example up to 50% by weight of the anhydride. The total amount of
glacial carboxylic acid is not critical but the total amount of anhydride or anhydride/acid
mixture is such that the ketoxime concentration is in most cases in the range of about
2 to 50% by weight at the start of the reaction.
[0032] The following examples further illustrate the invention.
Example 1
[0033] This example illustrates the preparation of 4-hydroxyacetophenone by the Fries rearrangement
of phenyl acetate using hydrogen fluoride as catalyst.
[0034] To a 300 cc Hastelloy C autoclave was charged 40.8 g (0.3 mol) of phenyl acetate.
The autoclave was sealed, immersed in a Dry Ice/isoprapanol bath and cooled internally
to -45°C, and evacuated to ca. 100 Torr (0.13 bar). Addition of 120 g (6.0 mol) of
anhydrous hydrogen fluoride was performed in a manner such as that the internal temperature
of the autoclave did not exceed 0°C. The internal pressure of the reactor was then
adjusted to 0 psig (1.1 bar) with nitrogen. The contents of the autoclave were stirred
and heated to 75°C for 1 h. The hydrogen fluoride was vented over a 45 min period
at ca. 45
0C. The mixture was poured onto 25 g of ice and neutralized with 45% potassium hydroxide
solution. The aqueous mixture was extracted with ethyl acetate. The organic fraction
was then dried over anhydrous magnesium sulfate, filtered, and the solvent was removed
on a rotary evaporator to yield 44.0 g of a dark green solid corresponding to 99.9%
conversion of phenyl acetate and 94.3% selectivity to 4-hydroxyacetophenone.
Example 2
[0035] This example illustrates the preparation of 4-hydroxyacetophenone by the Fries rearrangement
of phenyl acetate using hydrogen fluoride as catalyst with acetic anhydride as additive.
[0036] To a 300 cc Hastelloy C autoclave were added 30.6 grams (0.3 mole) of acetic anhydride.
The autoclave was cooled to -50°C and evacuated to 5 Torr (0.007 bar) whereupon 120
g (6.0 mole) of anhydrous hydrogen fluoride was transferred from a cylinder to the
autoclave. After the transfer of hydrogen fluoride was completed, the internal temperature
and the internal pressure of the autoclave was adjusted to -50°C and 1.1 bar using
nitrogen, respectively. To the stirred autoclave was added 81.6 g (0.6 mol) of phenyl
acetate at such a rate that the temperature of the mixture did not exceed -23
0C. Upon completion of phenyl acetate addition, the contents were warmed to 50°C and
stirred for 3 h during which time a pressure of ca. 40 psig (3.9 bar) was generated.
At the end of the run, the hydrogen fluoride was vented through a caustic scrubber
and the contents of the autoclave were poured onto ca. 30 g of ice. The pH of the
mixture was adjusted to 6.5 using 45% potassium hydroxide and the mixture was then
extracted with 75 ml of ethyl acetate (3x). The organic solution was dried over anhydrous
magnesium sulfate, filtered, and the solvent was removed using a rotary evaporator.
[0037] The reaction proceeded with 98.1% conversion of phenyl acetate and with the following
selectivities: phenol 1%, 4-hydroxyacetophenone (4-HAP) 82.3%; 2-hydroxyacetophenone
(2-HAP) 4.3%; 3-hydroxyacetophenone (3-HAP) 0.1%: 4-acetoxyacetophenone (4-AAP) 3.8%;
and 4-(4'-hydroxyl)-acetoptienone (HPAP) 0.4%.
Example 3
[0038] This example describes the formation of 4-hydroxyacetophenone by the Fries rearrangement
of phenyl acetate using hydrogen fluoride as catalyst and acetic acid as additive.
[0039] The procedure for Example 2 was repeated except that 18 grams (0.3 mole) of acetic
acid rather than acetic anhydride were charged to the reactor before it was cooled
and charged with the hydrogen fluoride. A conversion of 99.0% of phenyl acetate was
obtained with the following selectivities: phenol 3.3%; acetic acid 0.8%; 4-HAP 80.8%;
3-HAP 0; 2-HAP 5.8%; 4-AAP 0.3%; and HPAP 0.3%.
Example 4
[0040] This example illustrates the preparation of 4-hydroxyacetophenone (4HAP) by the Friedel-Crafts
acetylation of phenol with acetic acid as the acetylating agent.
[0041] Phenol (9.4 g, 0.1 moles) and acetic acid (12.0 g, 0.2 moles) were charged to a 300
ml Hastelloy C autoclave at room temperature. The reactor was evacuated and cooled
to -20
oC. HF (100 g, 5 moles) was then transferred into the reactor. The reactor was heated
to 80°C and maintained for 1 hour at reaction temperature. At the end of the reaction
the reactor was cooled to 20°C and the excess HF was vented to a KOH scrubber. Ethyl
acetate was added to the contents of the reactor. The mixture was then neutralized
with 45% aqueous KOH. The resulting organic phase was separated, dried over MgSO
4 and evaporated to afford a yellow solid which contained 13.1 g (0.096 moles) of 4-HAP.
Example 5
[0042] This example illustrates the formation of 4-hydroxyacetophenone oxime from 4-hydroxyacetophenone
and hydroxylamine hydrochloride
[0043] A solution was prepared by adding 13.6 g (0.1 mol) of 4-hydroxyacetophenone, 7.6
g (0.11 mol) of hydroxylamine hydrochloride, and 10 g of water to 40 mL of ethanol.
To the solution was added 5.0 g of 30% ammonium hydroxide which was then heated at
reflux for 2 h. The ethanol was removed on a rotary evaporator to yield a yellow oil.
An extractive work-up afforded 15.1 g (99%) of 4-hydroxyacetophenone oxime.
Example 6
[0044] This example illustrates the formation of 4-hydroxyacetcphenone oxime from 4-hydroxyacetophenone
and hydroxylamine sulfate.
[0045] A solution was prepared by adding 20.4 g (0.15 mol) of 4-hydroxyacetophenone and
13.0 g (0.08 mol) of hydroxylamine sulfate to 100 mL of water at 70°C. To the solution
was added 16.3 mL of 30% ammonium hydroxide which was then heated at reflux for 0.5
h. White crystals formed upon cooling yielding 21.0 g (92.6%) of 4-hydroxyacetophenone
oxime.
Example 7
[0046] This example illustrates the formation of 4-hydroxyacetophenone oxime from 4-hydroxyacetophenone
and hydroxylamine phosphate.
[0047] A solution was prepared by adding 20.4 g (0.15 mol) of 4-hydroxyacetophenone and
12.9 g (65.6 mmol) of hydroxylamine phosphate to 100 mL of water at 70°C. To the solution
was added 16.3 mL of 30% ammonium hydroxide which was then heated at reflux for 0.5
h. White crystals formed upon cooling yielding 21.0 g (92.6%) of 4-hydroxyacetophenone
oxime.
Examples
[0048] This example illustrates the formation of 4-acetoxyacetanilide (AAA) by the Beckmann
rearrangement and accompanying acetylation of 4-hydroxyacetophenone oxime using an
acidic ion-exchange resin as catalyst.
[0049] A mixture of 3.0 g (22.0 mmol) of 4-hydroxyacetophenone oxime, 3.0 of Amberlyst 15
(a sulfonic acid ion-exchange resin made by Rohm & Haas) , and 75 mL of a mixture
of glacial acetic acid and acetic anhydride (1:1) was heated at reflux under nitrogen
for 4 h. The ion-exchange resin was then removed and the acetic acid/acetic anhydride
was distilled in vacuo to yield yellow-white crystals. The crystals were dissolved
in ethyl acetate and treated with activated carbon and anhydrous magnesium sulfate.
The mixture as filtered and the solvent was removed on a rotary evaporator to yield
3.4 g (80.4%) of yellow crystals of 4-acetoxyacetanilide (AAA).
Example 9
[0050] This example illustrates the formation of 4-acetoxyacetanilide (AAA) by the Beckmann
rearrangement and accompanying acetylation of 4-hydroxyacetophenone oxime using methanesulfonic
acid as catalyst.
[0051] A solution of 10 g (66.2 mmol) of 4-hydroxyacetophenone oxime, 1.6 of 70% methanesulfonic
acid, 50 g of acetic anhydride and 100 g of glacial acetic acid was heated at reflux
under nitrogen for 2 h. Rotary evaporation of the solution yielded 17.0 g of light
brown crystals. Recrystallization from water yielded 6.7 g (52.4%) of 4-aoetoxyacetanilide
(AAA). The mother liquor contained 32.0% of AAA for a total yield of 84.4%.
Example 10
[0052] This example illustrates the formation of 4-acetoxyacetanilide (AAA) by the Beckmann
rearrangement and accompanying acetylation of 4-hydroxyacetophenone oxime using phosphoric
acid (H
3PO
4) as catalyst.
[0053] To a mixture of 100 g of glacial acetic acid,
50 g of acetic anhydride, and 3.6 g of 85% H
3PO
4, sparged with nitrogen for 30 minutes, was added 10 g of 4-hydroxyacetophenone oxime.
The mixture was heated at reflux for 1 hour under a nitrogen atmosphere, then cooled
to room temperature and neutralized with 13% Na
2CO
3. The mixture was evaporated to dryness using a rotary evaporator and the solid was
dissolved in 200 g of boiling water. After hot filtration, the solution was allowed
to cool and stand overnight. The ensuing white crystals were collected, washed with
20 mL of water, and dried in a vacuum oven (60°C/100 mm Hg (0.13 bar)) for 2 hours.
Upon drying, 9.4 g (73.9%) of white crystalline plates of 4-acetoxyacetanilide having
a melting point of 148-150°C was obtained. An additional 0.8 g of AAA and 1.5 g of
N-acetyl-para-aminophenol (APAP) were reclaimed from the mother liquor.
[0054] The procedures of examples 8 through 10 may also be used to prepare N-acetyl-(4-acetoxy-3-methylphenyl)
amine from o-cresyl acetate or o-cresol and acetic acid, and acetic anhydride; N-prcpionyl-(4-propionoxyphenyl
amine from phenyl prcpionate or phenol and propionic acid, and propionic anhydride;
and N-n-butyryl-(4-n-butyroxyphenyl) amine from phenyl n-butyrate or phenol and n-butyric
acid, and n-butyric anhydride, in the first and second reactions respectively.
[0055] The N-acyl-acyloxy aromatic amines, e.g. AAA, of this invention may be utilized as
monomers in the preparation of poly(ester-amide)s capable of forming an anisotropic
melt phase and suitable for being formed into shaped articles such as molded articles,
fibers and films, as shown, for example in U.S. Patent Nos. 4,330,457; 4,339,375;
4,341,688; 4,351,918; and 4,355,132.
[0056] The N-acyl-acyloxy aromatic amines of this invention, e.g. AAA, may also be hydrolyzed
to form the corresponding N-acyl-hydroxy aromatic amine, e.g. N-acetyl-para-aminophenol
(APAP) which is one of the most widely used over-the-counter analgesics. The following
example illustrates this process:
Example 11
[0057] A mixture of 5 g (25.9 mmol) of 4-acetoxyacetanilide (AAA), 1.4 g of 70% methanesulfonic
acid, and 50 g of water was heated at reflux for 1 h. Upon cooling, white crystals
formed. Analysis (GLC) of the crystals as well as the aqueous solution indicated 90%
conversion of the AAA to N-acetyl-para-aminophenol (APAP).
Example 12
[0058] This example illustrates the formation of N-acetyl-para-aminophenol by the Beckmann
rearrangement of 4-hydroxyacetophenone oxime using an acidic ion-exchange resin as
catalyst.
[0059] A mixture of 3.0 g of Amberlyst 15 (a sulfonic acid ion-exchange resin made by Rohm
& Haas), 3.0 g (22.0 mmol) of 4-hydroxyacetophenone oxime, and 50 mL of acetic acid
was heated at reflux under nitrogen for 2 h. The ion exchange resin was then removed
and the acetic acid was distilled in vacuo to afford an orange residue. The residue
was dissolved in ethanol and treated with activated carbon and anhydrous magnesium
sulfate. Removal of the ethanol using a rotary evaporator produced 2.9 g of a yellow
oil, which upon drying afforded 2.0 g (66.7%) of N-acetyl-para-aminophenol.
Example 13
[0060] This example illustrates the formation of N-acetyl-para-aminophenol by the Beckmann
rearrangement of 4-hydroxyacetophenone oxime using trifluoroacetic acid as catalyst.
[0061] A solution of 10 g (66.2 mmol) of 4-hydroxyacetophenone oxime and 75 g of trifluoroacetic
acid was heated at reflux under a nitrogen atmosphere. The trifluoroacetic acid was
then removed in a rotary evaporator to afford 14.7 g of oil which was dissolved in
100 mL of water. Upon cooling to 0°C for 0.5 h, crystallization occurred. Filtration
and drying of the crystals yielded 7.1 g (71%) of N-acetyl-para-aminophenol.
Example 14
[0062] This example illustrates the formation of N-acetyl-para-aminophenol by the Beckmann
rearrangement of 4-hydroxyacetophenone oxime using thionyl chloride in liquid sulfur
dioxide as catalyst.
[0063] A pressure battle (cooled in a CO
2/acetone bath) was charged with 50 mL of S02, 0.05 mL of SOC1
2, and 15 g of 4-hydroxyacetcphenone oxime. The CO
2/acetone bath was removed and the contents of the pressure bottle stirred for 1.5
h at room temperature. the S0
2 was then vented and the crystals washed from the pressure bottle with 50 mL of warm
water. The pH of the aqueous slurry was adjusted to 6.5 by dropwise addition of 30%
NH
4OH. The slurry was cooled in an ice bath and then filtered. The filtered crystals
were washed with 10 mL of ice water and dried overnight in a vacuum oven (60°C/100
mm Hg (0.13 bar)) yielding 13.3 g (88.7%) of white crystals of N-acetyl para-aminophenol
having a melting point of 166.5-170°C.
[0064] The procedures of examples 12 through 14 may also be used to prepare N-acetyl-(4-hydroxy-3-methylphenyl)
amine from o-cresyl acetate or o-cresol and acetic acid; N-propionyl-para-aminophenol
from phenyl propionate or phenol and propionic acid; and N-n-butyryl-para-aminophenol
from phenyl n-butyrate or phenol and n-butyric acid.
Example 15
[0065] A 250 ml pressure bottle was first cooled in a Dry Ice/acetone bath and was then
charged with 50 ml of SO
2 (via vacuum transfer), 0.05 mL of SOC1
2, and 15 g of 4-hydroxyacetophenone oxime. The Dry Ice/acetone bath was removed and
the contents of the pressure bottle stirred for 1.5 h. at roan temperature. The SO
2 was then vented and the crystals washed from the pressure bottle with 50 mL of warm
water. The pH of the aqueous slurry was adjusted to 6.5 by the dropwise addition of
concentrated ammonium hydroxide. The slurry was cooled in an ice bath and then filtered.
The filtered crystals were washed with 10 mL of ice water and dried overnight in a
vacuum oven at 60°C, yielding 13.3 g of white N-acetyl para-aminophenol crystals with
a melting point of 166.5-1
70oC.
Examples 16
[0066] The same general procedure as Example 15 was employed except that tap water (24°C)
was used to wash the crystals frcm the pressure bottle. Also, the amount of SOCl
2 was increased to 0.1 ml and the reaction time was decreased to 25 minutes. Off-white
crystals of N-acetyl para-aminophenol (13.7 g) were recovered with a melting point
of 165-169°C.
Example 17
[0067] This exanple illustrates the preparation of 2-methyl-4-hydroxyacetanilide using thionyl
chloride as the catalyst in S0
2.
[0068] The same general procedure as in Exanple 15 was employed except that 2-methyl-4-hydroxyacetophenone
oxime was employed as the oxime, the amount of oxime was reduced to 5 g, the amount
of thionyl chloride was increased to 0.5 mL, and the reaction time was decreased to
one hour at room temperature (24°C). Tan colored crystals of 2-methyl-4-hydroxyacetanilide
(1 g) were recovered with a melting point of 122-128°C.
Example 18
[0069] This example illustrates the preparation of 2-hydroxyacetanilide by the Beckmann
rearrargement of 2-hydroxyacetophenone oxime using thionyl chloride as the catalyst
in SO
2.
[0070] The same general procedure as Example 15 was employed except that the oxime was 2-hydroxyacetophenone
oxime, the amount of oxime was reduced to 5 g, the amount of thionyl chloride was
increased to 2.5 mL, the reaction time was decreased to 45 minutes, and the reaction
temperature was 30
oC. Yellow-colored crystals of 2-hydroxyacetanilide (3.6 g) was recovered with a melting
point of 201-203°C.
Example 19
[0071] This example illustrates the preparation of N-acetyl para-aminophenol by the Beckmann
rearrangement of 4-hydroxyacetophenone using thionyl chloride as catalyst in diethyl
ether.
[0072] A 250 ml round-bottom flask equipped and addition funnel was charged with 5 g of
4-hydroxyacetophenone oxime dissolved in 50 mL of anhydrous diethyl ether. A solution
of 0.5 mL of thionyl chloride in 15 mL of ether was then added dropwise from the addition
funnel. The contents of the flask were stirred during the addition and for an additional
30 minutes after completion of the addition. The ether was then removed on a rotovap.
The solid residue was then dissolved in 25 mL of hot water. The pH of the solution
was adjusted to about 6.5 with ammonium hydroxide and subsequently the solution was
cooled in an ice bath. The crystals which were formed were filtered and washed with
approximately 10 mL of ice water and then dried in a vacuum oven at 65
0C overnight. Brown crystals of N-acetyl para-aminophenol (1.1 g) were obtained with
a melting point of 161-2°C.
Example 20
[0073] This example illustrates the preparation of N-acetyl para-aminophenol from 4-hydroxyacetophenone,
using thionyl chloride as the catalyst in ethyl acetate.
[0074] The same procedure as Example 19 was employed except that ethyl acetate was used
as the solvent instead of diethyl ether. Light brown crystals of N-acetyl para-aminophenol
(1.9 g) with a melting point of 158-161°C were recovered.
Example 21
[0075] This example illustrates the preparation of N-acetylated para-aminophenol from 4-hydroxyacetophenone
using thionyl chloride as catalyst in acetone.
[0076] The same procedure as Example 19 was employed except that acetone was used as the
solvent instead of diethyl ether. Brown crystals of N-acetyl para-aminophenol (3.7
g) with a melting point of 159-161°C were recovered.
Example 22
[0077] This example illustrates the preparation of N-acetyl para-aminophenol from 4-hydroxyacetophenone
oxime using thionyl chloride as catalyst in tetrahydrofuran.
[0078] The same procedure as Example 19 was employed except that tetrahydrofuran was used
as the solvent instead of diethyl ether. Tan crystals of N-acetyl para-aminophenol
(2.5 g) with a melting point of 156-8°C were recovered.
Example 23
[0079] This example illustrates the preparation of N-acetyl para-aminophenol from 4-hydroxyacetophenone
oxime using thionyl chloride as the catalyst in methylene chloride.
[0080] The same procedure as Example 19 was employed but methylene chloride was used as
the solvent instead of diethyl ether. Dark brown crystals of N-acetyl para-aminophenol
(2.7 g) with a melting point of 152-156°C were obtained.
Example 24
[0081] This example illustrates the preparation of N-acetyl para-aminophenol from 4-hydroxyacetophenone
oxime using thionyl chloride as catalyst in acetone, under vacuum conditions.
[0082] The same procedure as Example 19 was employed except that acetone was used as the
solvent instead of diethyl ether and the system was run under vacuum ( 360 mm Hg (0.48
bar)). Tan crystals of N-acetyl para-aminophenol (3.6 g) with a malting point of 162-164°C
were obtained.
Example 25
[0083] This example illustrates the fact that the process of the present invention is capable
of producing nearly quatitative yields of the desired N-acyl-hydroxy aromatic amine.
[0084] The same general procedure as Example 16 was employed except that the filtrage was
also analyzed for N-acetyl para-aminophenol to determine the actual product yield.
The recovered solid weight 13.7 g and the filtrate contained an additional 0.7 g.
of N-acetyl para-aminophenol. Therefore, a yield of 97 percent was realized.